1. Field of the Invention
This invention relates to an improvement on the conventional rotating head assembly adapted for use, for example, in a magnetic video recording/reproducing apparatus or the like.
2. Description of the Prior Art
Portable video tape recorders have become popular as a result of efforts to reduce the size of rotating head type magnetic video recording/reproducing device. To meet this tendency, efforts have been exerted also to reduce the size and thickness of the rotating head assemblies to be used for the portable video tape recorders. Such efforts, however, are now approaching a structurally allowable limit.
Further, there have appeared rotating head type magnetic video recording/reproducing apparatuses of the kind having a camera combined therewith. The apparatuses of this kind are more strongly desired to have further reduction in size and weight. Typical examples of the conventional head assemblies used for such video tape recorders and video tape recorders of another type having a camera combined therewith are as described below:
FIG. 1 of the accompanying drawing shows the example of the conventional rotating head assembly, which is of an upper drum rotating system. Referring to FIG. 1, a fixed lower drum 1 has a rotation shaft 2 disposed in the middle part thereof. The rotation shaft 2 is rotatably mounted on the fixed lower drum 1 by means of bearings 3 and 4. A rotating upper drum 5 which is opposed to the fixed lower drum 1 is mounted on a support member 6 by mounting screws 7. The support member 6 is secured to the rotation shaft 2 by a mounting screw 8 and is disposed above the bearing 3. The rotating upper drum 5 is thus arranged to be rotatable relative to the fixed lower drum 1. At least one head base plate 10 which has a magnetic head 9 is mounted on the rotating upper drum 5 by means of screws 11. A travelling face 12 for a magnetic tape is formed on the peripheral faces of the rotating upper drum 5 and the fixed lower drum 1. To the support member 6 is attached a rotating-side winding 13 of a rotary transformer. Meanwhile, a stationary-side winding 14 of the rotary transformer is attached to the fixed lower drum 1 and is opposed to the winding 13. The winding 13 is connected to the magnetic head 9. Incoming or outgoing signals to or from the magnetic head 9 is arranged to go through the electromagnetic coupling of the rotary transformer.
Another support member 15 is mounted on the rotation shaft 2 and is disposed below the bearing 4. A rotary yoke 17 of a motor 16 is mounted on the support member 15 by means of a screw 18. A rotary magnet 19 is secured to the rotary yoke 17. A stator 20 and a stator coil 21 are secured to the fixed lower drum 1 and are opposed to the rotary magnet 19. The fixed lower drum 1 is mounted on a mount 22 which is disposed within a magnetic video recording/reproducing apparatus. The upper part of the rotating head assembly 24 which is arranged in this manner is covered by a cover 25 of the magnetic video recording/reproducing apparatus.
In a magnetic video recording/reproducing apparatus using a rotating head assembly which is arranged as shown in FIG. 1, the rotating upper drum 5 is mounted on the rotation shaft 2 and the rotation shaft is arranged to be carried by the bearings 3 and 4. Such being the arrangement, if the spacing distance between these bearings 3 and 4 is short, the rotation locus of the magnetic head 9 would be greatly affected and would be prevented from making a precise rotation by a tilt of the rotation shaft 2 resulting from deviation of these bearings 3 and 4 from their prescribed relative positions. Because of this problem, it has been extremely difficult to reduce the thickness of the rotating head assembly in the axial direction thereof.
In addition to this problem, the adjustment of the height, angle and protruding extent of the magnetic head 9 relative to the fixed lower drum 1 is difficult. Accordingly, even in cases where some parts must be replaced due to a damage of the magnetic head 9, the work required for this is not limited to mere replacement work on the parts but the height, etc. of the magnetic head 9 must be readjusted. The conventional rotating head assembly thus has been presenting another problem in terms of interchangeability of parts and this has been hindering to improvement in serviceability.
Further, in the case of the assembly shown in FIG. 1, the mounting screw 23 is tightened by inserting a screw driver into a space between the motor 16 and the mount 22. However, the space is too small to facilitate the work. In some cases, the mounting screw is arranged to be tightened from the surface side of the mount 22. In such a case, however, the various mechanisms arranged round the fixed lower drum 1 have worsened the workability.
In the case of a system having a camera combined into one unified body with the rotating head type magnetic video recording/reproducing apparatus, the optical path of the optical system of the camera must be obtained by avoiding the various parts of the rotating head type video recording/reproducing apparatus. This has been hindering attempts to reduce the size of the system. Besides, in such a system, driving means for automatically carrying out a focusing operation by driving an automatic focusing mechanism or driving means for driving a zoom lens to automatically carry out adjustment of a focal point occupies a large space to present a further hindrance to reduction in size.
The rotating head assembly 24 is disposed in the middle part of the magnetic video recording/reproducing apparatus. Besides, on the periphery of the assembly, there are arranged a magnetic tape travel guide, a loading mechanism for pulling the magnetic tape out of a cassette and for placing it on the rotating head assembly 24, etc. Therefore, a cover 25 is generally carried by a peripheral part of the magnetic video recording/reproducing apparatus to keep it away from the rotating head assembly 24. The cover must have a sufficient strength against external pressure which might be applied from outside as indicated by an arrow A. Even if the cover 25 is deformed and bent inward by the external pressure, the cover must be prevented from coming into contact with the rotating head assembly 24. Therefore, in the conventional system of this type, the thickness of the cover 25 is arranged to be thick and the cover is disposed sufficiently away from the rotating head assembly 24. This also has been hindering reduction in size and weight of a magnetic video recording/reproducing apparatus.
FIG. 2 shows an example of the conventional rotating head assembly of a head-on-propeller rotating system. The components similar to those shown in FIG. 1 are indicated by the same reference numerals as those used in FIG. 1. A cylindrical fixed upper drum 26 and a fixed lower drum 1 are fixed in prescribed relative positions by a coupling member 27 and mounting screws 28 and 29. The peripheral faces of the two drums 26 and 1 are arranged to serve as tape travelling surface 12. A guide 30 which guides a magnetic tape (which is not shown) is formed on the peripheral face of the fixed lower drum 1. At the common center of the two drums 1 and 26, there is provided a rotation shaft 2. The rotation shaft 2 is rotatably mounted on the fixed lower drum 1 by means of bearings 3 and 4. A head bar 31 is secured to the rotation shaft 2 by a screw 8. A head plate 32 is fitted on the head bar 31 and is secured thereto. At least one head base plate 10 which has a magnetic head 9 is secured to the head plate 32 by means of mounting screws 11.
In the lower part of the rotation shaft 2, a support member 15 is secured to the rotation shaft 2 in such a manner as to expel the plays of the bearings 3 and 4 in the axial direction of the rotation shaft. With this arrangement, the bearings 3 and 4 have a pre-load imposed thereon. The rotary yoke 15 of a motor 16 is secured to the support member 15 by means of a mounting screw 18. A rotary magnet 19 and a magnet sensor 33 for detecting the position of the magnetic head 9 are mounted on the rotary yoke 15. A stator 20 and a stator coil 21 are secured to the fixed lower drum 1 and are opposed to the rotary magnet 19. A reference numeral 34 indicates a printed circuit board for the motor 19; and 35 indicates a sensor for detecting the phase of the rotary magnet 19. The magnet sensor 33 is arranged not only to detect the position of the magnetic head 9 but also to detect the rotating state of the magnetic head 9 for controlling the normal rotating state of the head 9.
The rotating head assembly of the head-on-propeller rotating system which is arranged as described above with reference to FIG. 2 also has the same shortcomings as the rotating head assembly of the upper-drum rotating system shown in FIG. 1. These shortcomings likewise have been hindering efforts to reduce the size and thickness of the rotating head assembly and, as a result of that, also have been hindering efforts to reduce the size and weight of the magnetic video recording/reproducing apparatus.
In the rotating head assembly described above, the fixed drum 26 and the fixed lower drum 1 are joined together at their peripheral parts by means of the coupling member 27. However, since this arrangement necessitates to tighten the mounting screws 28 and 29 from a lateral direction, the fixed upper drum 26 tends to be deformed by this lateral tightening force. Further, a very high degree of positional precision is required for retaining the two drums 26 and 1 in a prescribed relative positions. However, in the conventionally practiced method of adjusting the relative positions of them, thin washers measuring 5 to 6.mu. is inserted between the coupling member 27 and the drums 26 and 1 before tightening. Therefore, much time has been required for the adjustment work.
As described in the foregoing with reference to FIGS. 1 and 2, the conventional rotating head assemblies have been hindering the efforts to reduce the size and thickness thereof. As a result of that, reduction in size and weight of an apparatus using such a rotating head assembly has been difficult.